Ref #76: Pass program for performance gain

.gitignore

@@ -1,3 +1,4 @@
+*.iml
 .idea
 node_modules
 npm-debug.log

README.md

@@ -77,6 +77,7 @@ module.exports = {
 
     // enables type checked rules like 'for-in-array'
     // uses tsconfig.json from current working directory
+    // See the notes on when using this with Webpack watch runs
     typeCheck: false,
 
     // automatically fix linting errors
@@ -115,6 +116,33 @@ module.exports = {
 }
 ```
 
+### typeCheck and Webpack Watch mode
+Tslint will use a TypeScript program for typeChecked rules.  The TypeScript program will cache file sources
+when the program is created and therefore, the program needs to be recreated every watch run to pick
+up file changes.  This is accomplished using a Webpack plugin.  
+
+If you wish to use typeCheck in Webpack watch mode, you'll need to add the `TslintPlugin` to your Webpack config.
+
+```js
+var TslintPlugin = require('tslint-loader').TslintPlugin;
+
+module.exports = {
+    plugins: [
+        new TslintPlugin()
+    ],
+    module: {
+        rules: [
+            {
+                test: /\.ts$/,
+                enforce: 'pre',
+                loader: 'tslint-loader',
+                options: { typeCheck: true, /* Loader options go here */ }
+            }
+        ]
+    }
+}
+```
+
 ## License
 
 [MIT](http://www.opensource.org/licenses/mit-license.php)

index.js

@@ -13,6 +13,8 @@ var mkdirp = require('mkdirp');
 var rimraf = require('rimraf');
 var objectAssign = require('object-assign');
 var semver = require('semver');
+var TslintPlugin = require('./lib/TslintPlugin');
+var programInstance = require('./lib/programInstance');
 
 function resolveFile(configPath) {
   return path.isAbsolute(configPath)
@@ -63,7 +65,7 @@ function lint(webpackInstance, input, options) {
   var program;
   if (options.typeCheck) {
     var tsconfigPath = resolveFile(options.tsConfigFile);
-    program = Lint.Linter.createProgram(tsconfigPath);
+    program = programInstance.getProgram(tsconfigPath);
   }
 
   var linter = new Lint.Linter(lintOptions, program);
@@ -140,4 +142,4 @@ module.exports = function(input, map) {
   lint(this, input, options);
   callback(null, input, map);
 };
-
+module.exports.TslintPlugin = TslintPlugin;

lib/TslintPlugin.js

@@ -0,0 +1,8 @@
+var programInstance = require('./programInstance');
+
+function TslintPlugin () {}
+TslintPlugin.prototype.apply = function (compiler) {
+  compiler.plugin('done', programInstance.clearProgram);
+};
+
+module.exports = TslintPlugin;

lib/programInstance.js

@@ -0,0 +1,20 @@
+var Linter = require('tslint').Linter;
+
+var program;
+
+function getProgram(configFile,
+                    projectDirectory) {
+  if (program == null) {
+    program = Linter.createProgram(configFile, projectDirectory);
+  }
+  return program;
+}
+
+function clearProgram() {
+  program = null;
+}
+
+module.exports = {
+  getProgram: getProgram,
+  clearProgram: clearProgram
+};

test/webpack.config.js

@@ -1,6 +1,7 @@
 'use strict';
 
 var path = require('path');
+var TslintPlugin = require('../index').TslintPlugin;
 
 module.exports = function() {
   return {
@@ -10,6 +11,9 @@ module.exports = function() {
     resolve: {
       extensions: ['.ts']
     },
+    plugins: [
+      new TslintPlugin()
+    ],
     module: {
       rules: [
         {